1. Field of the Invention
This invention relates to an overload relay switch and, more specifically, to an overload relay switch having a reduced number of components, including not having springs, and less complex components.
2. Background Information
Relay switches, such as, but not limited to relay switches on motor starters, are used to interrupt power to a motor in the event of an over current condition. Typically, a power source provides electricity to the motor via a plurality of line conductors. A contactor switch assembly is disposed on the conductors and is structured to interrupt the circuit. That is, the contactor switch assembly has a plurality of switch members structured to move between a first, open configuration, wherein electricity cannot be communicated from the power source to the motor, and a second, closed configuration, wherein electricity is communicated from the power source to the motor. The plurality of switch members are moved between positions by a solenoid. The configuration of the contactor switch assembly is controlled by the relay switch. That is, the contactor switch assembly solenoid receives a command signal from the relay. As long as the command signal is being provided, the contactor switch assembly solenoid maintains the switch members in the second, closed configuration. If the command signal is interrupted, or otherwise not provided, the contactor switch assembly solenoid moves/maintains the switch members in the first, open configuration.
The command signal is generated in the relay switch. That is, the relay switch is structured to detect characteristics of the current in the line conductors and, if no over current condition exists, provide the command signal. Relay switches, typically, have two outputs; the command signal and a reset indicator. Within the relay switch there is a switch assembly with two pairs of electrical terminals and two switch members. When the first pair of electrical terminals are coupled by a switch member, i.e. in electrical communication, the command signal is provided to the contactor switch assembly. When the second pair of electrical terminals are coupled by a switch member, i.e. in electrical communication, an indicator signal is provided to the reset indicator. The switch members are structured to be in opposing configurations. That is, if the first contacts are closed, the second contacts are open and vice versa. Thus, the relay switch is either providing a command signal, and maintaining the contactor switch assembly in the closed configuration, or not providing the command signal, and causing the contactor switch assembly to move to the open configuration, while providing an indication that the relay needs to be reset.
Relay switches, such as, but not limited to, the relay switches disclosed in U.S. Pat. Nos. 4,528,539 and 4,520,244, relied primarily, but not exclusively, on mechanical devices to both detect an over current condition in the line conductors and to move the switch assembly switch members. That is, the device that detected an over-current condition and actuated the relay switch was a mechanical device. The mechanical devices typically relied upon the heat created during an over current condition to cause a bi-metal to warp. The bi-metal was disposed adjacent to, or coupled to, a mechanical link that would move in response to the overheated bi-metal and cause the overload relay assembly switch assembly to open the first pair of electrical terminals. The mechanical link typically acted upon a “snap switch” or “flipper blade.” The snap switch was the relay switch conducting switch member. The snap switch included a plurality of features, such as, but not limited to, openings, bends, creases, slits, and/or shaped portions. These features allowed the snap switch conducting member to, essentially, change configuration in response to a manual actuation; i.e. the snap switch conducting member would snap between two configurations. For example, the snap switch could be configured to bend to the right thereby making contact, and electrically engage, the first terminals. Upon actuation, e.g., applying pressure to a selected point on the snap switch, the features cause the snap switch to bend to the left, thereby disconnecting the first terminals. As noted above, opening the first terminal would stop the command signal to the contactor switch assembly and the contactor switch assembly would open. When the contactor switch assembly was open, the current through the relay switch would stop and the bi-metal member would cool. The relay could then be reset. The reset action could, for example, apply pressure to the snap switch causing the snap switch conducting member to return to the configuration wherein the first terminals were in electrical communication.
Resetting the relay was typically accomplished by a reset actuator, typically a button or lever, that extended through the relay housing. When manually actuated, the reset actuator engaged elements to the relay operating mechanism and repositioned those elements for normal operation. This would include moving the overload relay assembly switch assembly to the second configuration wherein the command signal was provided and the contactor switch assembly would close. Thus, resetting the relay would also allow electricity to be provided to the motor. The reset actuator was typically structured to engage various mechanical elements of the relay operating assembly and often had a complex shape. For example, the actuator typically included one or more radial extensions and/or flanges that were structured to engage and move other components within the relay. Further, the reset switch was typically biased to the tripped position (the position the reset actuator was in after an over current condition) by a spring. The complex shape and spring loading of the reset switch added complexity and assembly costs to relay switches.
It is further noted that relay switches could include a test actuator in addition to, or combined with, the reset actuator. The test actuator included additional mechanical links that would cause the relay switch operating mechanism to trip, i.e. cause the overload relay assembly switch assembly to open the first pair of electrical terminals thereby simulating an over current condition. The relay switch could then be reset by the reset actuator or by reversing the actuation of the test actuator. That is, the test actuator typically operated on a pull-to-test, push-to-reset configuration. Like the reset actuator, a test actuator typically had a complex shape and was spring biased.
Further, as noted above, if the relay switch was a snap switch, the snap switch conductive member typically had a complex shape. This shape was required so as to accomplish the “snap” effect required of the snap switch conductive member. Further, the snap switch conductive member may also engage, contact, or otherwise interact with other components of the relay. Thus, the reset actuator, the test actuator, and the relay switch conductive member each had a complex shape. These components were expensive to manufacture and, due to having to place the members in the correct position so as to interact with the other components, were expensive to install.